Buffy died, So Kendra was called. When Kendra died, Faith was called. Faith was then in a Coma because Buffy stabbed her. Buffy is alive, Therefore no other slayers would be called.
The Watchers council knows that Buffy was brought back to life. They also know about Faith being in a coma. So they wouldn't send another Slayer because Buffy is alive. If both Buffy and Faith died, Then another Slayer would be called and another Watcher would be sent to train her.
The whole line of Slayers from Buffy on has been altered because Xander saved her. If Buffy had remained dead then Kendra would become the only Slayer. If Kendra had been killed by Drusilla or anyone else, Than Faith would have been called. Now the question is, Since Faith was in a coma, If Faith was put in a coma due to different circumstances, Would they call another Slayer? - Faith wouldn't be able to continue her slayer duties if she was comatose.
The whole slayer thing is confusing!